Pipeline systems are widely used in the long distance transmission of various fluids such as petroleum and natural gas products and can be laid above and/or below ground. Since pipelines are typically exposed to weathering, corrosion is a major problem which must be handled. Generally, corrosion monitors are used and regular physical inspections are undertaken according to need. In certain instances, however, physical inspection is often difficult, particularly when the line is wholly or partially underground. Leaks are particularly undesirable, especially when hazardous chemicals are transported and land adjacent the pipeline is developed.
Corrosion can result when moisture from the surrounding environment comes in contact with the surface of the pipeline. This is a particularly acute problem in warm, humid regions where rainfall is high and temperature differentials between the transported material and ambient can cause moisture condensation on the pipeline surface.
Efforts to prevent moisture-related corrosion have typically employed a hydrophobic coating such as oil applied to the exterior surface of the pipeline to form a waterproof barrier. In addition, the oil can be gelled to prevent coating loss.
Materials Protection and Performance 11(1):42-43, Pipeline Gas Journal, January, 1972, describes the use of gelled fuel oil as a corrosion barrier coating. A buried pipeline was reportedly repaired and further corrosion inhibited by inserting a new, smaller-diameter pipe inside the old corroded pipeline, and pumping a high viscosity fuel oil containing a gelling agent and a pH control agent into the annulus between the old and new pipe. The fuel oil was gelled to a consistency of a heavy grease.
The use of petroleum-based barriers, however, has several drawbacks. For one thing, the mixture is relatively viscous and difficult to pump. For another, oil-based fluids are undesirable from an environmental perspective. In addition, the gelled oil is difficult to remove from the annulus if it becomes necessary to undertake a repair or dispose of the line.
Accordingly, there is a need for a method of inhibiting corrosion in a pipeline which uses a non-oil based, environmentally acceptable corrosion inhibitor, which can be pumped at a low viscosity, but will not leak or run after being put in place, and which, optimally, would be readily removable to facilitate repair and disposal.